Light exposure during night suppresses nocturnal increase in growth hormone secretion in Holstein steers
Light exposure during night suppresses nocturnal increase in growth hormone secretion in Holstein steers
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DOI：
10.2527/jas.2008-0877
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发表时间：
2008-08-01
影响因子：
3.3
通讯作者：
Sutoh, M.
中科院分区：
文献类型：
--
作者：
Kasuya, E.;Kushibiki, S.;Sutoh, M.
为了解牛GH分泌节律的调节机制及褪黑素（MEL）对GH分泌的调节作用，研究了黑白花阉牛白天和夜间的GH分泌规律及光刺激对夜间GH和MEL分泌的影响。将牛保持在12 h光照（LIGHT; 500 lx，0600至1800 h）：12 h黑暗（DARK; 10 lx，1800至0600 h）的恒定光照条件下。在Exp. 1，分别在LIGHT（1100至1500 h）和DARK（2300至0300 h）期间每隔15 min采血4 h。采样时间为0500 - 0900 h，采用通常的光照转换（光照开始时间为0600 h;早晨采样）。在Exp. 2、将阉牛从0000至0100 h暴露于光（500 lx）下1 h。分别用放射免疫法和酶免疫法测定血浆GH和MEL浓度。血浆GH（P < 0.05）和MEL（P < 0.01）浓度DARK组4 h均高于LIGHT组。另一方面，尽管MEL浓度在早晨0600的光照后降低，但GH释放没有改变。在DARK期间增加的GH分泌被光暴露1h抑制（P < 0.01），MEL浓度也是如此（P < 0.05）。松果体MEL受光照条件的影响，可能在牛GH分泌节律中起重要作用。
To understand the regulatory mechanism of the secretory rhythm of GH and the involvement of melatonin (MEL) in GH regulation in cattle, daytime and nighttime profiles of GH secretion and the effect of a photic stimulation on nocturnal GH and MEL secretion were investigated in Holstein steers. Steers were kept under a constant lighting condition of 12 h of light (LIGHT; 500 lx, 0600 to 1800 h): 12 h of dark (DARK; 10 lx, 1800 to 0600 h). In Exp. 1, blood was taken for 4 h at 15-min intervals during LIGHT (1100 to 1500 h) and DARK (2300 to 0300 h), respectively. The sampling was also performed from 0500 to 0900 h, with the usual light transition (light onset at 0600 h; morning sampling). In Exp. 2, steers were exposed to light (500 lx) for 1 h from 0000 to 0100 h. Plasma GH and MEL concentrations were determined by RIA and enzyme immunoassay, respectively. Both GH (P < 0.05) and MEL (P < 0.01) concentrations in plasma for 4 h during DARK were greater than those during LIGHT. On the other hand, although MEL concentrations were decreased after the light onset at 0600 during the morning, GH release was not altered. Increased GH secretion during DARK was suppressed (P < 0.01) by the 1 h of light exposure, as were MEL concentrations (P < 0.05). Pineal MEL, which was affected by the photic condition, may play an important role in the secretory rhythm of GH secretion in cattle.